Siren sensor systems for warning motor vehicle operators of an approaching siren sounding emergency vehicles of various types are disclosed in the prior art. Siren Sensor systems for controlling traffic control lights at intersections upon the detection of a siren sound for permitting an emergency vehicle to safely cross an intersection with the right of way are also disclosed in the prior art.
U.S. Pat. No. 5,278,553 Cornett et al discloses methods and apparatus for detecting siren sounds emitted by an emergency vehicle approaching from a distance to warn a motor vehicle operator of an approaching vehicle in sufficient time to permit the vehicle operator to take corrective action to permit the emergency vehicle to safely continue on its path.
U.S. Pat. No. 4,806,931, Nelson discloses an electronic system for the recognition of emergency siren signals for effecting control of traffic signal lights at an intersection in response to the detected siren sound to allow an emergency vehicle to travel through the intersection with the right of way. This electronic system is dependent on the recognition of different types of emergency vehicle siren sound patterns programmed into a microprocessor. The recognition of the different signal patterns is dependent on a recognition algorithm for an individual predetermined repetitive sound pattern. The output signal from this system signals the presence of a predetermined sound pattern and the direction of the sound pattern based on a multiplicity of directional microphones wherein the signal producing the largest output amplitude provides one directional information.
The Nelson U.S. Pat. No. 4,806,931 describes various operating modes for siren sounds and refers to other prior art system that are unique to certain siren sounds such as a “yelp” siren and not other types of siren warning sounds as is possible by the system of the '931 patent. The '931 system utilizes omni-directional microphone and four directional microphones corresponding to the directions north, south, east, and west relative to the intersection the emergency vehicle is approaching. The system is dependent on first determining if a siren sound pattern has been detected in order to initiate the directional processing of the detected signals as represented in FIG. 2 of the '931 patent.
U.S. Pat. No. 4,625,206, Jensen, also discloses an electronic system for providing directional control of traffic signals. The disclosed system is particularly suited to detecting “yelp” siren signals and is a relatively expensive circuit installation.
Another prior art technique for responding to siren sounds for warning a motor vehicle operator of an approaching emergency vehicle sounding its siren is disclosed in U.S. Pat. No. 4,785,474, Bernstein et al.
U.S. Pat. No. 5,495,242, Kick et al, discloses an early warning system for hearing impaired motor vehicle operators for warning the drivers of the proximity of an emergency vehicle. This is an attempt to detect all kinds of siren sounds by means of a single system. The '242 patent also describes an embodiment for pre-emptive traffic signal controller responsive to the detection of a siren sound for overriding a traffic light controller to insure that the siren sounding vehicle has a green light to proceed through an intersection and to stop cross traffic.
Despite the number of prior art systems based on the detection of the sound waves emitted from a siren, there is no known commercially available, reliable siren sensor system presently available for controlling traffic control lights at an intersection. Accordingly, there is a present need for a relatively inexpensive, reliable electronic processing system for controlling traffic control lights in favor of an emergency vehicle at an intersection to permit the vehicle to travel through the intersection with the only right of way.